Condensed Consolidated Statements Of Cash Flows (USD $) In Thousands	6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010
CASH FLOWS FROM OPERATING ACTIVITIES:
Consolidated net income	$ 34,587	$ 1,858
Adjustments to reconcile consolidated net income to net cash provided by (used in) operating activities:
Allocations of net income to limited partnership units and founding/working partner units	18,437	5,163
Fixed asset depreciation and intangible asset amortization	24,092	25,537
Employee loan amortization	16,213	18,545
Stock-based compensation	41,979	14,069
Sublease provision adjustment	4,244
Losses on equity investments	3,060	3,441
Deferred tax expense (benefit)	2,259	(3,521)
Recognition of deferred revenue	(1,105)	(2,466)
Other	1,678	834
(Increase) decrease in operating assets:
Cash segregated under regulatory requirements	(1,212)	(347)
Securities borrowed		(32,926)
Securities owned	(1,495)	922
Receivables from broker, dealers, clearing organizations, customers and related broker-dealers	(364,560)	(183,265)
Accrued commissions receivable, net	(45,888)	(36,890)
Receivables from related parties	(2,449)	1,619
Loans, forgivable loans and other receivables from employees and partners	(40,817)	(20,066)
Other assets	1,053	3,816
Increase (decrease) in operating liabilities:
Securities sold, not yet purchased		(11)
Payables to broker-dealers, clearing organizations, customers and related broker-dealers	345,929	202,766
Accrued compensation	(18,494)	44,526
Deferred revenue		914
Accounts payable, accrued and other liabilities	(19,067)	(19,342)
Payables to related parties	(2,576)	(56,066)
Net cash used in operating activities	(4,132)	(30,890)
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of fixed assets	(15,127)	(19,610)
Purchases of marketable securities		(3,002)
Capitalization of software development costs	(6,937)	(8,344)
Capitalization of trademarks, patent defense and registration costs	(468)	(440)
Investment in unconsolidated entities	(884)	(862)
Net cash used in investing activities	(23,416)	(32,258)
CASH FLOWS FROM FINANCING ACTIVITIES:
Collateralized borrowings, net	(2,768)	(2,914)
Long-term borrowings		(150,000)
Issuance of convertible notes		150,000
Repurchase of Class A common stock	(126)	(17,371)
Proceeds from offering of Class A common stock, net	13,590	17,792
Redemption of limited partnership interests	(468)	(28,901)
Proceeds from exercise of stock options	8,195
Tax impact on exercise/delivery of equity awards	2,760
Cancellation of restricted stock units in satisfaction of withholding tax requirements	(1,362)	(1,725)
Earnings distributions to limited partnership interests in BGC Holdings	(43,283)	(8,122)
Dividends to stockholders	(34,136)	(16,625)
Net cash used in financing activities	(57,598)	(57,866)
Effect of exchange rate changes on cash	7,281	(6,877)
Net decrease in cash and cash equivalents	(77,865)	(127,891)
Cash and cash equivalents at beginning of period	364,104	469,301
Cash and cash equivalents at end of period	286,239	341,410
Supplemental cash information:
Cash paid during the period for taxes	16,694	16,144
Cash paid during the period for interest	10,794	5,172
Supplemental non-cash information:
Conversion of Class B common stock into Class A common stock		6
Issuance of Class A common stock upon exchange of Cantor units	8,407
Issuance of Class B common stock upon exchange of Cantor units	$ 8,407